Upgrade to use stable `package:googleapis/v1.dart` of datastore

test/db/e2e/metamodel_test_impl.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library metamodel_test;
 
 import 'dart:async';
 
 import 'package:unittest/unittest.dart';
 
 import 'package:gcloud/datastore.dart';
-import 'package:gcloud/datastore.dart' show Key, Query, Partition;
+import 'package:gcloud/datastore.dart' show Key, Partition;
 import 'package:gcloud/db.dart' as db;
 import 'package:gcloud/db/metamodel.dart';
 
 List<Entity> buildEntitiesWithDifferentNamespaces() {
   newKey(String namespace, String kind, int id) {
     var partition = new Partition(namespace);
     return new Key([new KeyElement(kind, id)], partition: partition);
   }
 
   newEntity(String namespace, String kind, {int id: 1}) {
@@ skipping 73 matching lines @@
             return Future.wait(futures).then((_) {
               expect(datastore.commit(deletes: keys), completes);
             });
           });
         });
       });
     });
   });
 }